1. Field of the Invention
This invention relates to image processing methods and apparatuses that process image data representing lines having prescribed lengths and widths displayed on monitor screens.
This application claims priority on Japanese Patent Applications Nos. 2004-63889 and 2004-67348, the contents of which are incorporated herein by reference.
2. Description of the Related Art
Conventionally, various kinds of software programs have been developed to display a plurality of lines (or line segments) having prescribed lengths and widths on screens of monitors (or displays), wherein start-point coordinates and end-point coordinates of lines as well as widths of lines are designated by central processing devices (CPUs) to produce three data therefor, which are converted into dot data and are then written into frame buffers having storage capacities, which correspond to numbers of dots displayed on two-dimensional flat screens of monitors. Then, dot data stored in frame buffers are supplied to monitors (such as liquid crystal displays) so as to display lines on screens, wherein double-buffer configurations are arranged to realize read/write operations regarding dot data. This technology is disclosed in Japanese Patent Application Publication No. H04-175887, for example.
Normally, image processing apparatuses are each constituted by LSI devices, wherein frame buffers are incorporated into chips of LSI devices. However, fame buffers have relatively large storage capacities, which require relatively large chip areas. For this reason, it is preferable for image processing apparatuses not to incorporate frame buffers but to incorporate line buffers, each having a relatively small storage capacity corresponding to a limited number of dots on a single (horizontal) scanning line, in consideration of manufacturing costs and sizes, which should be reduced.
However, it takes a relatively long time to convert three pieces of data, representing start-point coordinates and end-point coordinates of lines as well as widths of lines, into dot data. Such processing executed by conventional line buffers having limited capacities may fail to precisely display lines having prescribed lengths and widths on monitor screens.
For example, a conventionally known image processing apparatus displays a line having a prescribed width, wherein a start-point terminal and an end-point terminal lie in parallel with or lie perpendicular to horizontal scanning lines on the monitor screen as shown in FIG. 19. This makes it very difficult to display a line having a prescribed width whose start-point terminal and end-point terminal lie perpendicular to the length direction as shown in FIG. 20.
When lines having prescribed widths are drawn without performing circular terminating processes on end portions thereof, end portions of lines should be deteriorated in appearances on monitor screens. In particular, when two lines are drawn to connect together on the monitor screen, they cannot be connected smoothly at the connecting area therebetween. Japanese Patent Application Publication No. S62-285188 teaches a solution to this problem, in which as shown in FIG. 21A, in which a circle is drawn at the connecting area between two lines, thus realizing smooth connection therebetween.
The aforementioned process is performed in such a way that a circle whose diameter matches the horizontal width of a line, which lies in parallel with horizontal scanning lines on the monitor screen, or the vertical width of a line, which lies perpendicular to horizontal scanning lines on the monitor screen, is drawn in the connecting area at which two lines are connected together. This causes a problem in that the diameter of the circle becomes greater than the horizontal width of the line or the vertical width of the line, whereby two lines cannot be connected smoothly on the monitor screen. In addition, the aforementioned circular terminating process is performed with respect to the connecting area, which is detected between two lines and in which a circle is drawn. That is, other ends of lines cannot be made smooth in appearance on the monitor screen. In addition, the circular terminating process requires a relatively great burden of load in the circuitry for automatically discriminating the connecting area between two lines.